1 /*- 2 * Copyright (c) 1982, 1986, 1989, 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * (c) UNIX System Laboratories, Inc. 5 * All or some portions of this file are derived from material licensed 6 * to the University of California by American Telephone and Telegraph 7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 8 * the permission of UNIX System Laboratories, Inc. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 4. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 35 */ 36 37 #include <sys/cdefs.h> 38 __FBSDID("$FreeBSD$"); 39 40 #include "opt_ktrace.h" 41 #include "opt_mac.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/sysproto.h> 46 #include <sys/eventhandler.h> 47 #include <sys/filedesc.h> 48 #include <sys/kernel.h> 49 #include <sys/kthread.h> 50 #include <sys/sysctl.h> 51 #include <sys/lock.h> 52 #include <sys/malloc.h> 53 #include <sys/mutex.h> 54 #include <sys/priv.h> 55 #include <sys/proc.h> 56 #include <sys/pioctl.h> 57 #include <sys/resourcevar.h> 58 #include <sys/sched.h> 59 #include <sys/syscall.h> 60 #include <sys/vmmeter.h> 61 #include <sys/vnode.h> 62 #include <sys/acct.h> 63 #include <sys/ktr.h> 64 #include <sys/ktrace.h> 65 #include <sys/unistd.h> 66 #include <sys/sx.h> 67 #include <sys/signalvar.h> 68 69 #include <security/audit/audit.h> 70 #include <security/mac/mac_framework.h> 71 72 #include <vm/vm.h> 73 #include <vm/pmap.h> 74 #include <vm/vm_map.h> 75 #include <vm/vm_extern.h> 76 #include <vm/uma.h> 77 78 79 #ifndef _SYS_SYSPROTO_H_ 80 struct fork_args { 81 int dummy; 82 }; 83 #endif 84 85 static int forksleep; /* Place for fork1() to sleep on. */ 86 87 /* 88 * MPSAFE 89 */ 90 /* ARGSUSED */ 91 int 92 fork(td, uap) 93 struct thread *td; 94 struct fork_args *uap; 95 { 96 int error; 97 struct proc *p2; 98 99 error = fork1(td, RFFDG | RFPROC, 0, &p2); 100 if (error == 0) { 101 td->td_retval[0] = p2->p_pid; 102 td->td_retval[1] = 0; 103 } 104 return (error); 105 } 106 107 /* 108 * MPSAFE 109 */ 110 /* ARGSUSED */ 111 int 112 vfork(td, uap) 113 struct thread *td; 114 struct vfork_args *uap; 115 { 116 int error; 117 struct proc *p2; 118 119 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); 120 if (error == 0) { 121 td->td_retval[0] = p2->p_pid; 122 td->td_retval[1] = 0; 123 } 124 return (error); 125 } 126 127 /* 128 * MPSAFE 129 */ 130 int 131 rfork(td, uap) 132 struct thread *td; 133 struct rfork_args *uap; 134 { 135 struct proc *p2; 136 int error; 137 138 /* Don't allow kernel-only flags. */ 139 if ((uap->flags & RFKERNELONLY) != 0) 140 return (EINVAL); 141 142 AUDIT_ARG(fflags, uap->flags); 143 error = fork1(td, uap->flags, 0, &p2); 144 if (error == 0) { 145 td->td_retval[0] = p2 ? p2->p_pid : 0; 146 td->td_retval[1] = 0; 147 } 148 return (error); 149 } 150 151 int nprocs = 1; /* process 0 */ 152 int lastpid = 0; 153 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 154 "Last used PID"); 155 156 /* 157 * Random component to lastpid generation. We mix in a random factor to make 158 * it a little harder to predict. We sanity check the modulus value to avoid 159 * doing it in critical paths. Don't let it be too small or we pointlessly 160 * waste randomness entropy, and don't let it be impossibly large. Using a 161 * modulus that is too big causes a LOT more process table scans and slows 162 * down fork processing as the pidchecked caching is defeated. 163 */ 164 static int randompid = 0; 165 166 static int 167 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 168 { 169 int error, pid; 170 171 error = sysctl_wire_old_buffer(req, sizeof(int)); 172 if (error != 0) 173 return(error); 174 sx_xlock(&allproc_lock); 175 pid = randompid; 176 error = sysctl_handle_int(oidp, &pid, 0, req); 177 if (error == 0 && req->newptr != NULL) { 178 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 179 pid = PID_MAX - 100; 180 else if (pid < 2) /* NOP */ 181 pid = 0; 182 else if (pid < 100) /* Make it reasonable */ 183 pid = 100; 184 randompid = pid; 185 } 186 sx_xunlock(&allproc_lock); 187 return (error); 188 } 189 190 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 191 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 192 193 int 194 fork1(td, flags, pages, procp) 195 struct thread *td; 196 int flags; 197 int pages; 198 struct proc **procp; 199 { 200 struct proc *p1, *p2, *pptr; 201 struct proc *newproc; 202 int ok, trypid; 203 static int curfail, pidchecked = 0; 204 static struct timeval lastfail; 205 struct filedesc *fd; 206 struct filedesc_to_leader *fdtol; 207 struct thread *td2; 208 struct sigacts *newsigacts; 209 int error; 210 211 /* Can't copy and clear. */ 212 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 213 return (EINVAL); 214 215 p1 = td->td_proc; 216 217 /* 218 * Here we don't create a new process, but we divorce 219 * certain parts of a process from itself. 220 */ 221 if ((flags & RFPROC) == 0) { 222 if ((p1->p_flag & P_HADTHREADS) && 223 (flags & (RFCFDG | RFFDG))) { 224 PROC_LOCK(p1); 225 if (thread_single(SINGLE_BOUNDARY)) { 226 PROC_UNLOCK(p1); 227 return (ERESTART); 228 } 229 PROC_UNLOCK(p1); 230 } 231 232 vm_forkproc(td, NULL, NULL, flags); 233 234 /* 235 * Close all file descriptors. 236 */ 237 if (flags & RFCFDG) { 238 struct filedesc *fdtmp; 239 fdtmp = fdinit(td->td_proc->p_fd); 240 fdfree(td); 241 p1->p_fd = fdtmp; 242 } 243 244 /* 245 * Unshare file descriptors (from parent). 246 */ 247 if (flags & RFFDG) 248 fdunshare(p1, td); 249 250 if ((p1->p_flag & P_HADTHREADS) && 251 (flags & (RFCFDG | RFFDG))) { 252 PROC_LOCK(p1); 253 thread_single_end(); 254 PROC_UNLOCK(p1); 255 } 256 *procp = NULL; 257 return (0); 258 } 259 260 /* 261 * Note 1:1 allows for forking with one thread coming out on the 262 * other side with the expectation that the process is about to 263 * exec. 264 */ 265 if (p1->p_flag & P_HADTHREADS) { 266 /* 267 * Idle the other threads for a second. 268 * Since the user space is copied, it must remain stable. 269 * In addition, all threads (from the user perspective) 270 * need to either be suspended or in the kernel, 271 * where they will try restart in the parent and will 272 * be aborted in the child. 273 */ 274 PROC_LOCK(p1); 275 if (thread_single(SINGLE_NO_EXIT)) { 276 /* Abort. Someone else is single threading before us. */ 277 PROC_UNLOCK(p1); 278 return (ERESTART); 279 } 280 PROC_UNLOCK(p1); 281 /* 282 * All other activity in this process 283 * is now suspended at the user boundary, 284 * (or other safe places if we think of any). 285 */ 286 } 287 288 /* Allocate new proc. */ 289 newproc = uma_zalloc(proc_zone, M_WAITOK); 290 #ifdef MAC 291 mac_init_proc(newproc); 292 #endif 293 #ifdef AUDIT 294 audit_proc_alloc(newproc); 295 #endif 296 knlist_init(&newproc->p_klist, &newproc->p_mtx, NULL, NULL, NULL); 297 STAILQ_INIT(&newproc->p_ktr); 298 299 /* We have to lock the process tree while we look for a pid. */ 300 sx_slock(&proctree_lock); 301 302 /* 303 * Although process entries are dynamically created, we still keep 304 * a global limit on the maximum number we will create. Don't allow 305 * a nonprivileged user to use the last ten processes; don't let root 306 * exceed the limit. The variable nprocs is the current number of 307 * processes, maxproc is the limit. 308 */ 309 sx_xlock(&allproc_lock); 310 if ((nprocs >= maxproc - 10 && 311 priv_check_cred(td->td_ucred, PRIV_MAXPROC, SUSER_RUID) != 0) || 312 nprocs >= maxproc) { 313 error = EAGAIN; 314 goto fail; 315 } 316 317 /* 318 * Increment the count of procs running with this uid. Don't allow 319 * a nonprivileged user to exceed their current limit. 320 * 321 * XXXRW: Can we avoid privilege here if it's not needed? 322 */ 323 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, SUSER_RUID | 324 SUSER_ALLOWJAIL); 325 if (error == 0) 326 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 327 else { 328 PROC_LOCK(p1); 329 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 330 lim_cur(p1, RLIMIT_NPROC)); 331 PROC_UNLOCK(p1); 332 } 333 if (!ok) { 334 error = EAGAIN; 335 goto fail; 336 } 337 338 /* 339 * Increment the nprocs resource before blocking can occur. There 340 * are hard-limits as to the number of processes that can run. 341 */ 342 nprocs++; 343 344 /* 345 * Find an unused process ID. We remember a range of unused IDs 346 * ready to use (from lastpid+1 through pidchecked-1). 347 * 348 * If RFHIGHPID is set (used during system boot), do not allocate 349 * low-numbered pids. 350 */ 351 trypid = lastpid + 1; 352 if (flags & RFHIGHPID) { 353 if (trypid < 10) 354 trypid = 10; 355 } else { 356 if (randompid) 357 trypid += arc4random() % randompid; 358 } 359 retry: 360 /* 361 * If the process ID prototype has wrapped around, 362 * restart somewhat above 0, as the low-numbered procs 363 * tend to include daemons that don't exit. 364 */ 365 if (trypid >= PID_MAX) { 366 trypid = trypid % PID_MAX; 367 if (trypid < 100) 368 trypid += 100; 369 pidchecked = 0; 370 } 371 if (trypid >= pidchecked) { 372 int doingzomb = 0; 373 374 pidchecked = PID_MAX; 375 /* 376 * Scan the active and zombie procs to check whether this pid 377 * is in use. Remember the lowest pid that's greater 378 * than trypid, so we can avoid checking for a while. 379 */ 380 p2 = LIST_FIRST(&allproc); 381 again: 382 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 383 while (p2->p_pid == trypid || 384 (p2->p_pgrp != NULL && 385 (p2->p_pgrp->pg_id == trypid || 386 (p2->p_session != NULL && 387 p2->p_session->s_sid == trypid)))) { 388 trypid++; 389 if (trypid >= pidchecked) 390 goto retry; 391 } 392 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 393 pidchecked = p2->p_pid; 394 if (p2->p_pgrp != NULL) { 395 if (p2->p_pgrp->pg_id > trypid && 396 pidchecked > p2->p_pgrp->pg_id) 397 pidchecked = p2->p_pgrp->pg_id; 398 if (p2->p_session != NULL && 399 p2->p_session->s_sid > trypid && 400 pidchecked > p2->p_session->s_sid) 401 pidchecked = p2->p_session->s_sid; 402 } 403 } 404 if (!doingzomb) { 405 doingzomb = 1; 406 p2 = LIST_FIRST(&zombproc); 407 goto again; 408 } 409 } 410 sx_sunlock(&proctree_lock); 411 412 /* 413 * RFHIGHPID does not mess with the lastpid counter during boot. 414 */ 415 if (flags & RFHIGHPID) 416 pidchecked = 0; 417 else 418 lastpid = trypid; 419 420 p2 = newproc; 421 p2->p_state = PRS_NEW; /* protect against others */ 422 p2->p_pid = trypid; 423 AUDIT_ARG(pid, p2->p_pid); 424 LIST_INSERT_HEAD(&allproc, p2, p_list); 425 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 426 sx_xunlock(&allproc_lock); 427 428 /* 429 * Malloc things while we don't hold any locks. 430 */ 431 if (flags & RFSIGSHARE) 432 newsigacts = NULL; 433 else 434 newsigacts = sigacts_alloc(); 435 436 /* 437 * Copy filedesc. 438 */ 439 if (flags & RFCFDG) { 440 fd = fdinit(p1->p_fd); 441 fdtol = NULL; 442 } else if (flags & RFFDG) { 443 fd = fdcopy(p1->p_fd); 444 fdtol = NULL; 445 } else { 446 fd = fdshare(p1->p_fd); 447 if (p1->p_fdtol == NULL) 448 p1->p_fdtol = 449 filedesc_to_leader_alloc(NULL, 450 NULL, 451 p1->p_leader); 452 if ((flags & RFTHREAD) != 0) { 453 /* 454 * Shared file descriptor table and 455 * shared process leaders. 456 */ 457 fdtol = p1->p_fdtol; 458 FILEDESC_LOCK_FAST(p1->p_fd); 459 fdtol->fdl_refcount++; 460 FILEDESC_UNLOCK_FAST(p1->p_fd); 461 } else { 462 /* 463 * Shared file descriptor table, and 464 * different process leaders 465 */ 466 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 467 p1->p_fd, 468 p2); 469 } 470 } 471 /* 472 * Make a proc table entry for the new process. 473 * Start by zeroing the section of proc that is zero-initialized, 474 * then copy the section that is copied directly from the parent. 475 */ 476 td2 = FIRST_THREAD_IN_PROC(p2); 477 478 /* Allocate and switch to an alternate kstack if specified. */ 479 if (pages != 0) 480 vm_thread_new_altkstack(td2, pages); 481 482 PROC_LOCK(p2); 483 PROC_LOCK(p1); 484 485 bzero(&p2->p_startzero, 486 __rangeof(struct proc, p_startzero, p_endzero)); 487 bzero(&td2->td_startzero, 488 __rangeof(struct thread, td_startzero, td_endzero)); 489 490 bcopy(&p1->p_startcopy, &p2->p_startcopy, 491 __rangeof(struct proc, p_startcopy, p_endcopy)); 492 bcopy(&td->td_startcopy, &td2->td_startcopy, 493 __rangeof(struct thread, td_startcopy, td_endcopy)); 494 495 td2->td_sigstk = td->td_sigstk; 496 td2->td_sigmask = td->td_sigmask; 497 498 /* 499 * Duplicate sub-structures as needed. 500 * Increase reference counts on shared objects. 501 */ 502 p2->p_flag = 0; 503 if (p1->p_flag & P_PROFIL) 504 startprofclock(p2); 505 mtx_lock_spin(&sched_lock); 506 p2->p_sflag = PS_INMEM; 507 /* 508 * Allow the scheduler to adjust the priority of the child and 509 * parent while we hold the sched_lock. 510 */ 511 sched_fork(td, td2); 512 513 mtx_unlock_spin(&sched_lock); 514 p2->p_ucred = crhold(td->td_ucred); 515 td2->td_ucred = crhold(p2->p_ucred); 516 #ifdef AUDIT 517 audit_proc_fork(p1, p2); 518 #endif 519 pargs_hold(p2->p_args); 520 521 if (flags & RFSIGSHARE) { 522 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 523 } else { 524 sigacts_copy(newsigacts, p1->p_sigacts); 525 p2->p_sigacts = newsigacts; 526 } 527 if (flags & RFLINUXTHPN) 528 p2->p_sigparent = SIGUSR1; 529 else 530 p2->p_sigparent = SIGCHLD; 531 532 p2->p_textvp = p1->p_textvp; 533 p2->p_fd = fd; 534 p2->p_fdtol = fdtol; 535 536 /* 537 * p_limit is copy-on-write. Bump its refcount. 538 */ 539 p2->p_limit = lim_hold(p1->p_limit); 540 541 pstats_fork(p1->p_stats, p2->p_stats); 542 543 PROC_UNLOCK(p1); 544 PROC_UNLOCK(p2); 545 546 /* Bump references to the text vnode (for procfs) */ 547 if (p2->p_textvp) 548 vref(p2->p_textvp); 549 550 /* 551 * Set up linkage for kernel based threading. 552 */ 553 if ((flags & RFTHREAD) != 0) { 554 mtx_lock(&ppeers_lock); 555 p2->p_peers = p1->p_peers; 556 p1->p_peers = p2; 557 p2->p_leader = p1->p_leader; 558 mtx_unlock(&ppeers_lock); 559 PROC_LOCK(p1->p_leader); 560 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 561 PROC_UNLOCK(p1->p_leader); 562 /* 563 * The task leader is exiting, so process p1 is 564 * going to be killed shortly. Since p1 obviously 565 * isn't dead yet, we know that the leader is either 566 * sending SIGKILL's to all the processes in this 567 * task or is sleeping waiting for all the peers to 568 * exit. We let p1 complete the fork, but we need 569 * to go ahead and kill the new process p2 since 570 * the task leader may not get a chance to send 571 * SIGKILL to it. We leave it on the list so that 572 * the task leader will wait for this new process 573 * to commit suicide. 574 */ 575 PROC_LOCK(p2); 576 psignal(p2, SIGKILL); 577 PROC_UNLOCK(p2); 578 } else 579 PROC_UNLOCK(p1->p_leader); 580 } else { 581 p2->p_peers = NULL; 582 p2->p_leader = p2; 583 } 584 585 sx_xlock(&proctree_lock); 586 PGRP_LOCK(p1->p_pgrp); 587 PROC_LOCK(p2); 588 PROC_LOCK(p1); 589 590 /* 591 * Preserve some more flags in subprocess. P_PROFIL has already 592 * been preserved. 593 */ 594 p2->p_flag |= p1->p_flag & P_SUGID; 595 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 596 SESS_LOCK(p1->p_session); 597 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 598 p2->p_flag |= P_CONTROLT; 599 SESS_UNLOCK(p1->p_session); 600 if (flags & RFPPWAIT) 601 p2->p_flag |= P_PPWAIT; 602 603 p2->p_pgrp = p1->p_pgrp; 604 LIST_INSERT_AFTER(p1, p2, p_pglist); 605 PGRP_UNLOCK(p1->p_pgrp); 606 LIST_INIT(&p2->p_children); 607 608 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 609 610 #ifdef KTRACE 611 /* 612 * Copy traceflag and tracefile if enabled. 613 */ 614 mtx_lock(&ktrace_mtx); 615 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 616 if (p1->p_traceflag & KTRFAC_INHERIT) { 617 p2->p_traceflag = p1->p_traceflag; 618 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 619 VREF(p2->p_tracevp); 620 KASSERT(p1->p_tracecred != NULL, 621 ("ktrace vnode with no cred")); 622 p2->p_tracecred = crhold(p1->p_tracecred); 623 } 624 } 625 mtx_unlock(&ktrace_mtx); 626 #endif 627 628 /* 629 * If PF_FORK is set, the child process inherits the 630 * procfs ioctl flags from its parent. 631 */ 632 if (p1->p_pfsflags & PF_FORK) { 633 p2->p_stops = p1->p_stops; 634 p2->p_pfsflags = p1->p_pfsflags; 635 } 636 637 /* 638 * This begins the section where we must prevent the parent 639 * from being swapped. 640 */ 641 _PHOLD(p1); 642 PROC_UNLOCK(p1); 643 644 /* 645 * Attach the new process to its parent. 646 * 647 * If RFNOWAIT is set, the newly created process becomes a child 648 * of init. This effectively disassociates the child from the 649 * parent. 650 */ 651 if (flags & RFNOWAIT) 652 pptr = initproc; 653 else 654 pptr = p1; 655 p2->p_pptr = pptr; 656 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 657 sx_xunlock(&proctree_lock); 658 659 /* Inform accounting that we have forked. */ 660 p2->p_acflag = AFORK; 661 PROC_UNLOCK(p2); 662 663 /* 664 * Finish creating the child process. It will return via a different 665 * execution path later. (ie: directly into user mode) 666 */ 667 vm_forkproc(td, p2, td2, flags); 668 669 if (flags == (RFFDG | RFPROC)) { 670 atomic_add_int(&cnt.v_forks, 1); 671 atomic_add_int(&cnt.v_forkpages, p2->p_vmspace->vm_dsize + 672 p2->p_vmspace->vm_ssize); 673 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 674 atomic_add_int(&cnt.v_vforks, 1); 675 atomic_add_int(&cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 676 p2->p_vmspace->vm_ssize); 677 } else if (p1 == &proc0) { 678 atomic_add_int(&cnt.v_kthreads, 1); 679 atomic_add_int(&cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 680 p2->p_vmspace->vm_ssize); 681 } else { 682 atomic_add_int(&cnt.v_rforks, 1); 683 atomic_add_int(&cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 684 p2->p_vmspace->vm_ssize); 685 } 686 687 /* 688 * Both processes are set up, now check if any loadable modules want 689 * to adjust anything. 690 * What if they have an error? XXX 691 */ 692 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 693 694 /* 695 * Set the child start time and mark the process as being complete. 696 */ 697 microuptime(&p2->p_stats->p_start); 698 mtx_lock_spin(&sched_lock); 699 p2->p_state = PRS_NORMAL; 700 701 /* 702 * If RFSTOPPED not requested, make child runnable and add to 703 * run queue. 704 */ 705 if ((flags & RFSTOPPED) == 0) { 706 TD_SET_CAN_RUN(td2); 707 setrunqueue(td2, SRQ_BORING); 708 } 709 mtx_unlock_spin(&sched_lock); 710 711 /* 712 * Now can be swapped. 713 */ 714 PROC_LOCK(p1); 715 _PRELE(p1); 716 717 /* 718 * Tell any interested parties about the new process. 719 */ 720 KNOTE_LOCKED(&p1->p_klist, NOTE_FORK | p2->p_pid); 721 722 PROC_UNLOCK(p1); 723 724 /* 725 * Preserve synchronization semantics of vfork. If waiting for 726 * child to exec or exit, set P_PPWAIT on child, and sleep on our 727 * proc (in case of exit). 728 */ 729 PROC_LOCK(p2); 730 while (p2->p_flag & P_PPWAIT) 731 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 732 PROC_UNLOCK(p2); 733 734 /* 735 * If other threads are waiting, let them continue now. 736 */ 737 if (p1->p_flag & P_HADTHREADS) { 738 PROC_LOCK(p1); 739 thread_single_end(); 740 PROC_UNLOCK(p1); 741 } 742 743 /* 744 * Return child proc pointer to parent. 745 */ 746 *procp = p2; 747 return (0); 748 fail: 749 sx_sunlock(&proctree_lock); 750 if (ppsratecheck(&lastfail, &curfail, 1)) 751 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 752 td->td_ucred->cr_ruid); 753 sx_xunlock(&allproc_lock); 754 #ifdef MAC 755 mac_destroy_proc(newproc); 756 #endif 757 #ifdef AUDIT 758 audit_proc_free(newproc); 759 #endif 760 uma_zfree(proc_zone, newproc); 761 if (p1->p_flag & P_HADTHREADS) { 762 PROC_LOCK(p1); 763 thread_single_end(); 764 PROC_UNLOCK(p1); 765 } 766 tsleep(&forksleep, PUSER, "fork", hz / 2); 767 return (error); 768 } 769 770 /* 771 * Handle the return of a child process from fork1(). This function 772 * is called from the MD fork_trampoline() entry point. 773 */ 774 void 775 fork_exit(callout, arg, frame) 776 void (*callout)(void *, struct trapframe *); 777 void *arg; 778 struct trapframe *frame; 779 { 780 struct proc *p; 781 struct thread *td; 782 783 /* 784 * Finish setting up thread glue so that it begins execution in a 785 * non-nested critical section with sched_lock held but not recursed. 786 */ 787 td = curthread; 788 p = td->td_proc; 789 td->td_oncpu = PCPU_GET(cpuid); 790 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 791 792 sched_lock.mtx_lock = (uintptr_t)td; 793 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); 794 CTR4(KTR_PROC, "fork_exit: new thread %p (kse %p, pid %d, %s)", 795 td, td->td_sched, p->p_pid, p->p_comm); 796 797 /* 798 * Processes normally resume in mi_switch() after being 799 * cpu_switch()'ed to, but when children start up they arrive here 800 * instead, so we must do much the same things as mi_switch() would. 801 */ 802 803 if ((td = PCPU_GET(deadthread))) { 804 PCPU_SET(deadthread, NULL); 805 thread_stash(td); 806 } 807 td = curthread; 808 mtx_unlock_spin(&sched_lock); 809 810 /* 811 * cpu_set_fork_handler intercepts this function call to 812 * have this call a non-return function to stay in kernel mode. 813 * initproc has its own fork handler, but it does return. 814 */ 815 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 816 callout(arg, frame); 817 818 /* 819 * Check if a kernel thread misbehaved and returned from its main 820 * function. 821 */ 822 if (p->p_flag & P_KTHREAD) { 823 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 824 p->p_comm, p->p_pid); 825 kthread_exit(0); 826 } 827 mtx_assert(&Giant, MA_NOTOWNED); 828 829 EVENTHANDLER_INVOKE(schedtail, p); 830 } 831 832 /* 833 * Simplified back end of syscall(), used when returning from fork() 834 * directly into user mode. Giant is not held on entry, and must not 835 * be held on return. This function is passed in to fork_exit() as the 836 * first parameter and is called when returning to a new userland process. 837 */ 838 void 839 fork_return(td, frame) 840 struct thread *td; 841 struct trapframe *frame; 842 { 843 844 userret(td, frame); 845 #ifdef KTRACE 846 if (KTRPOINT(td, KTR_SYSRET)) 847 ktrsysret(SYS_fork, 0, 0); 848 #endif 849 mtx_assert(&Giant, MA_NOTOWNED); 850 } 851